Telegraph system



M. B. KERR April 26, 1932.

TELEGRAPH SYSTEM Filed Oct. 5, 1929 a 8 5 cm a 8 8 mm RLRWHEU Liiwrqiiwqr J l r mm {m 5 ma m nm @m m gm mv mm m mmw m 8 N 5 o & .m a 9 o m F i J av mv S 2 lg n N" m NM m m R ow Q ow T fl mfi& Lu 4 mm wm kt 6m 6 INVENTOR MARK s. KERR BY J 64 ATTORNEY Patented Apr. 26, 1932 UNiTEfi dlitTES PATENT OFFICE MARK B. KERR, OF GRASMERE, NEW YORK, ASSIGNOR TO INTERNATIONAL COMMUNI- CATIONS LABORATORIES II'JCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK TELEGRAZPH SYSTEM Application filed October 5, 1929. Serial No. 397,514.

This invention relates to (printing) telegraph systems particularly suited for operation over long lines or submarine cables. In the transmission of telegraph signals over submarine cables the shorter signalling impulses are attenuated more than the longer ones and if the speed of transmission be sutficiently high, separated impulses of unit length may not attain sufficient amplitude even after amplification to operate the receiving relays. The apparatus and circuits accordin to this invention prevent the loss of these impulses and restore them to their full amplitude in their proper time or phase relation with the remainder of the signals, at the same time giving the maximum operating margins on the receiving distributor segments. I

Previous inventions relating to vibrating and signal interpolating relays make use of one or more line relays under the joint control of the incoming line. signals and a series of impulses locally generated, the latter being regulated both as to amplitude and phase to control the relays only during the signal intervals in which the current received from the line or cable is too weak to operate the relays. The present invention makes use of a selective principle in which the line relays, arranged in accordance with the normal two relay cable receiving circuit, operate in accordance with the incoming line signals, and an auxiliary relay cooperating with said relays performs the function of filling in the lost or attenuated impulses which are too weak to operate the said relays.

The two relay receiving circuit, well understood in the art, consists of two polarized relays LS and LM having their line windings 7 and 12 connected in series with their polarities respectively reversed, and with their biasing windings 8 and 13 connected in series to a source of battery supply 28 so that the relays are normally held on their inoperative (or spacing) contacts when no current is flowing in the line windings. In normal operation the current in the biasing windings 8 and 13 is adjusted to half the strength of the current in the line windings, so that whenever the current formerly flowing through the line windings in series dies away, the biasing windings become effective to restore the operated relay to inoperative position by moving its armatureagainst its spacing contact. In the embodiment disclosed in the drawing, relay LS is so connected that it will operate responsive to negative impulses applied to its iine winding 7 over conductor 6, and relay LM will operate responsive to positive imaulses applied to its line winding 12 over conductor 6.

In this invention single unit impulses are supplied locally whenever the line relays are both in the normal (inoperative) position, and the biasing circuit common to the line relays is closed intermittently through a series of distributor segments in the receiving distributor rings, which segments are normally unused so that the line relays, when operated by the line signals can only restore in a definite time or phase relation with re spect to the operation of the printer magnets (or signal storing relays) and the auxiliary or interpolating relay. The advantage of this is that it permits the maximum possible receiving margins or range independent of the length of the segments in the auxiliary distributor rings through which the auxiliary relay is positioned.

One object of: this invention is a simple, eflicient and economical system for correctly recording the signals which are attenuated in the process of transmission from the transmitting station.

Another object is to increase the receiving range. Other objects will appear from the specification.

In accordance with this invention the received amplified signals are impressed upon the line windings of two line relays, connected in series but with their polarities reversed, the other windings of the relays are connected in a biasing circuit to restore them during the intervals when the line current falls below the operating value. The lost or attenuated impulses are then inserted in their correct phase relation and polarity by a third relay which operates in accordance with the combined signals as selectively generated by itself and the two, line relays. The comically set forth.

The signals transmitted by the transmitting station, incoming over the conductor or cable 1 are connected to the input circuit of the amplifier 4. A suitable impedance net work consisting of a condenser 2 and an in- Y ductance 3, may be introduced in circuit with the cable 1 and the input of the amplifier 4. The line windings 7 and 12, of the polarized line relays LS and LM connected in series,

and with polarities reversed, are connected 'via conductors 5 and 6 with the output C11- cuit of the amplifier 4, so that any signal impulse received over the cable 1 and amplified by the amplifier 4 will be impressed upon the line windings 7 and 12 of the line relays. If the impulse transmitted from the sending station is a single unit impulse it may be so attenuated owing to the electrical constants of the cable 1, that it will not be received at the receiving station, or if received and amplified, nevertheless fails to produce a sufficient change in the current in the windings 7 and 12 of the line relays LS and LM, to cause either of said relays to operate.

Any form of distributor may be used at the receiving station. In the drawing a distributor consisting of a series of concentric rings 38, 59 etc., is illustrated. The rings 38 and 59 which are unbroken, are the common rings, while certain other rings consist of a plurality of insulated segments 4041, 6061, and so forth. The brushes 39 and 69 are caused to rotate in predetermined fixed relation, the brush 39 serving to alternately connect feed ring 38 with the segment 4011,

' and the brush 69 similarly serving to alternately connect ring 59 with the segments 6061.

In normal printing telegraph operation the receiving rings 59 with segments 60 and 61 are arranged with the receiving segments 61 shorter than the sending segments at the transmitting end) so that only the central portion of the incoming signals are utilized. The intervening segments 60, not connected to the magnets 62 to 68, would normally be left unconnected. These segments 60 are known in the art as dead segments.

It should be observed that whenever brush 39 connects feed ring 38 with a segment 40,

the grounded windings 43 and 44 of relay LV are connected in series with condenser 37 to ground at 36. Similarly whenever brush 39 is connected to a segment 41 condenser 37 is connected via conductor 27 to a source of current supply under control of the armatures and contacts of one or more of the relays LM, LS and LV.

Brushes 39 and 69 rotate continuously and in synchronism with the signals incoming over the cable 1. In the drawing, brush 39 has rotated to the position indicated by the dotted line, at which point it has completed a circuit to operate relay LV as follows: from ground at 36, condenser 37, common ring 38, brush 39, se ment 40, conductor 42, windings 43 and 44 of relay LV in series, conductor 48, resistance 34 to groundf It should be understood that condenser 37 was formerly charged positively during the time when the brush 39 was connecting preceding segment 41 to common ring 33 over the following circuit: from ground at 36, condenser 37, common ring 38, segment 41, conductor 27, armature and left hand contact 9 of relay LS, conductor 17, armature and left hand contact 14 of relay LM, conductors 19 and 50, armature 46 and left hand contact 45 of relay LV, conductor 49, resistance 33, positive battery 32 to ground. When the discharge circuit for condenser 37 is closed, as shown in the drawing, relay LV operates and armature 46 moves from left to right opening the circuit formerly closed at its left hand contact 45 and connecting negative battery 30 to segment 41 preparatory to closing a circuit for charging condenser 37 negatively in the manner hereinafter described.

Relay LV operated closes the circuit to opcrate the printer relay PR as follows: from negative battery 30, resistance 31, right hand contact 47 and armature 46 of relay LV, conductors 50 and 19, left hand contact 14 and armature 15 of relay LM, conductor 17, left hand contact 9 and armature 10 of relay LS, conductors 22 and 23, windings 53 and 52 of relay PR in series, conductor 26, resistance 35 to ground. Relay PR operated, moves its armature 55 from its left hand contact 54, to its right hand contact 56 but performs no useful function at this time.

Simultaneously with the positioning of brush 39 upon segment 40, brush 69 was positioned upon segment 60 as indicated by the dotted line in the drawing. With brush 69 so positioned a circuit is closed through the holding or biasing windings 13 and 8 of relays LM and LS respectively, as follows: from the positive bus-bar of battery 28, variable resistance 21, conductor 20, windings 13 and 8 of relays LM and LS in series, conductor 71, segment 60, brush 69, common ring 59, conductor 70 to the negative bus-bar of battery 23. The direction of the current flowing in the windings 13 and 3 is such as to tend to hold armatures 15 and 10 against their respective left hand contacts 14 and 9, (or to cause the said armatures to assume their respective left hand po sition, provided no current is flowing at this time in the line windings 7 and 12, if the said armatures had previously been operated to some other position, for example, the right hand position). The continued rotation of the distributor causes brushes 39 and 69 to be advanced from segments 40 and 60 to segments 41 and 61 respectively. With the brush 39 advanced until positioned upon segment 41, the following circuit will be 3 closed to charge condenser 37 negatively:

from grounded battery 30, resistance 31, conductor 51, right hand contact 47 and armature 46 of relay LV, conductors 50 and 19, left hand contact 14 and armature 15 of r relay LM, conductor 17, left hand contact charge the condenser and re-operate relay LV, thereby causing armature46 to move from right hand contact 47 to left hand contact 45 thereby closing a circuit to re-operate relay PR, and move its armature from right to left opening contact 56 and closing contact 54. 7

With brush 69 connecting segment 61 to common ring 59 while the armature 55 of the PR relay was held against right hand contact 56, the following circuit was closed to energize electro-magnet 66, (which as heretofore stated may be either a storing relay or a printer magnet) from negative bus-bar of battery 28, conductor 70, common ring 59, brush 69, segment 61, winding of electro-magnet 66, conductors 7 6 and 57 right hand contact 56 and armature 55 of the PR relay, resistance coil 29 to the positive bus-bar of battery 28. Electro-magnet 66 energized will function to store the impulse either electrically or mechanically dependent upon whether the electro-mag'net 66 is a storing relay or a printer magnet, which in turn will depend upon the particular use to which the invention is put.

It thus appears that the continued rotation of the brushes 39 and 69 of the distributor will cause the condenser 37 to be successively charged and discharged, being charged positively, followed by its discharge through the windings of the relay LV to move armature 46 of relay LV from one position to the other, and then negatively followed by its subsequent discharge through the windings of relay LV move armature 46 to its alternate position. This cycle of operations continues without interruption unless an impulse received over the cable 1, and amplified by the amplifier 4 causes one of the line relays LM or LS to operate in the manner hereinafter described. It further appears that so long as the distributor performs its cycle of operations without interference due to the operation of one of the relays LM or LS responsive to a received impulse, the relay PR will continue to move its armature from left to right and from right to left in succession, thereby generating a series of impulses of unit length, whereby alternate electro-magnets some of which are indicated at 62 to 68 inclusive will be operated in succession.

It was heretofore assumed that the impulses received over the cable 1 were unit impulses, that is, impulses of alternate polarity impressed upon the cable 1 for time intervals each equivalent to the passage of the sending brushes over a single segment. WVhen an impulse of a'given polarity is impressed upon the cable 1 for two or more units of time, or while the sending brush is passing over two or more successive sending segments, the impulse is said to be a two (or more) unit impulse.

Assuming that a two (or more) unit impulse is impressed upon the cable 1, such an impulse although distorted due to the electrical constants of the cable, will be received at the receiving station at least in part, and will be amplified by the amplifier 4, so as to cause a current of a magnitude sufficient to operate one of the relays LM or LS, as the case may be, to be impressed upon the output circuit of the amplifier 4, which includes the line windings 7 and 12 of relays LS and LM respectively. With the brushes 39 and 69 positioned as indicated in the drawing, the phase relation to the incoming signals is such that the latter portion of the previous signal impulse, if two or more units length, is still flowing in the line windings of relays LS and LM and one or other is operated. The theoretical end of the signal, which is the point when the polarity changes from positive to negative or vice versa, occurs if perfect synchronism exists when the brushes 39 and 69 are at the middle points of segments 40 and 60, re spectively. Assuming that the previous signal was a single unit of positive polarity, relays LM and LS were both on their left hand contacts and condenser 37 was charged positively from contact 45 of LV as previously described. As the brushes rotate over segments 40 and respectively, from the posi tion shown in the drawing, LV is operated to its right hand contact, the biasing circuit to relays LM and LS is closed through seg ment 60, and relay PR is operated to its right hand contact. Assuming that the next impulse will be a negative one of two or more units length, negative current will start to flow in lead 6 of the amplifier output justas brushes 39 and 69 pass the middle points of segments 40 and 60 respectively. This current will tend to operate relay LS to its right hand contact and hold relay LM on its left hand contact. Relay LS does not operate immediately, however, because the biasing circuit, tending to hold relays LM and LS on their left hand contacts, is still closed through segment 60 and brush 69. As the brushes 39 and 69 reach the ends of their respective segments 40 and 60, the condenser will have completely discharged through the wine ings of relay LV and the negative current in line Winding 7 of relay LS will have increased in amplitude sufficiently to cause relay LS to operate. as its tongue 10 moves away from contact 9, the circuit from negative battery through contacts a? and l6 of relay LV to the windings of relay PR is broken, but condenser 2% in series with resistance 25 permits current to continue flowing in the windings of relay PR momentarily, thus preventing it from breaking its contact 56. Contact 10 o" relay LS now makes its contact 11, and closes the circuit from negative battery direct to the windings of relay PR. This holds contact 56 of relay PR closed, and discharges condenser 24-. Brushes 39 and 69, continuing their rotation now pass onto segments 4-1 and (31 respectively. The condenser 32'' is charged negatively from contact 11 of relay LS and the printer magnet (or storing relay) 66 operates on current received from contact 56 of printer relay PR. While the brushes pass over the remainder of segments ll and 61, relay LS remains operated under the in fluence of the line current. hen the brush cs reach the next segments a0 and $0, the negative charge on condenser 37 operates relay TLV to its left hand contact 45, andcharges condenser 2 1-. The latter performs no useful function at this time. Brush 69 coming in contact with segment 60 closes the biasing circuit of relays LS and LM, but relay LS remains operated due to the predominance of line current in its line winding 7. The biasing current in winding 13 of relay LM is in the same direction the line current in the winding 12, so that the magnetic pulls of ti e two currents add in this relay and hold its tongue 15 firmly against contact i l.

The brushes 39 and 69, continuing their rotation, reach the second segments 41 and 61 with the conditions unchanged, as relay LS still remains operated. In this case magnet 67 will not operate as its op rating circuit is held open at contact 5 of relay PR, and relay LV is held on its left .iand contact by the negative discharge of condenser 3'7. lVhen the brus us reach the thirc segments 40 and 60, the line current in relays LM and LS will begin to fall off, if the impulse was only of two units length. In that case, t e biasing current, which is now flowing again, through segment 60, will restore relay soon as the line current has fallen oil sufficiently to permit the biasing current to prcdominate. As it opens contact 11, the discharge of condenser 24 holds relay PR on its contact 56 momentarily. hen the tongue 10 of relay LS is restored to contact 9, positive battery through contacts 45 and l6 of relay LV, operates relay PR to its contact 5 in the circuit previously traced, and completely discharges condenser 24. From the above description it is that the circuit to the printer magnets from the contacts of PR is always prepared for the next impuls of reverse polarity before the impulse has actually arr' red, so that if the next impulse is only a single unit and thereby attenuated it will not be lost in the receiving circuit. In like manner can the circuits involving the operation of relay LM on positive impulses of two or more units length be traced.

N ow let us assume that the brushes are behind their proper (or theoretical) phase, this is the same as saying that the line signals are ahead of the brushes, and is the condition which obtains when the receiving brushes are oriented or adjusted to the backward limit of the p inting marg n or range. Let us sums, for example, that the impulse previous in phase to the position 015 brushes shown on the drawing was a long positive impulse and that it is followed immediately with a negative two unit impulse. With the brushes in their correct phase, the cross over of current from positive to negative would occur when the brushes reach the middle of the segments ll) and 60, on the front edges of which they are shown resting. lVithth brushes behind the signals in phase, the cross over of line current from positive to negative will occur when the brushes are still on segments 41 and 61 just ahead of the position shown in the drawing. The condition that exists just as the line current changes from positive to neg-c tive is as follows: relay LM still remains on its right hand contact, since no current is flowing in biasing winding, rclays LS and PR are on their left hand contacts, relay LV on its right hand contact, and condenser 37 charged positively. As the line current takes an appreciable time to build up in the negative direction after the cross over, due to the slope of the wave, relay LM does not restore to its left hand contact and relay LS does not operate to its right hand contact to cause relay PR to reverse its position until the brushes have reached the position shown in the drawing. Thus, by the arrangement of this invention, which delays the restoring of the line relays until the brushes have reached the desired phase relation, so as not to clip the impulses impressed on the printer it is possible to record the signals properly even though the signals are so far ahead in phase that the polarity cross over of the line current occurs While the brush 69 is on one of the segments 61.

As soon as relay LM restores and relay LS operates, the printer relay PR is positioned according to a negative incoming impulse.

tlin

Even if relay LS had not operated at the time as above described, because of the beginning of a new biasing impulse from segment 60, the instant relay LM restores the circuit would have been closed through to the contacts of relay LV, which would have operated the relay PR to its right hand contact the same as if it had been operated direct from relay LS. In other words, the first unit of every incoming impulse is filled in by the relay LV, and the proper operation of the circuit on this first unit is independent of the line relays.

Now consider the case when the brushes are ahead of their proper phase and assume that the same group of impulses are received as heretofore described. The long positive impulse that exists prior to the time the brush 69 reaches the position shown is now late in dropping oif to zero. Let us assume that the phase relation is such as to bring the cross over from positive to negative line current after the brushes 39 and 69 have passed from segments 40 and 60 and are at some point in the first half of the succeeding segments ll and 61. In this case the limiting condition is that relay LM must restore be fore brush 69 leaves segment 60 and breaks the restoring circuit. As soon as relay LM restores, the negative battery from the contacts of relay LV becomes eii'ective to op crate relay PR and repeat the proper selecting impulse into the printer magnet connected to segment 61. Also, the same negative battery from relay LV charges the condenser 37 through segment ll to reverse the position of relay LV on the following segment 40.

It is seen from this that the application of the biasing current to the line relays intermittently, through segments 650 permits a maximum receiving range of one sending segment less the diiference in phase as measured in brush travel between the non-operative position of the line relays at the backward limit of phase relation between the brushes and incoming signals, and the operative position of the relays at the forward limit of the phase relation. The non-operative and operative positions of the relays are both determined by the difference between the line current and biasing current which occurs at the end of a line impulse of two or more units length as the current starts to fall off to zero.

What is claimed is:

1. The method of restoring an unbiased telegraph line relay from its operative position to its inoperative position which comprises operating the telegraph recording apparatus by part of an impulse locally generated and utilizing the remainder of said impulse to energize a coil in said line relay.

2. In a telegraph system, a line relay, recording means, a local circuit and a distributor having a plurality of segmented rings,

alternate segments of one of said rings being arranged to operate "said recording means and other segments intervening phase relation with the previously mentioned alternate segments being connected through said local circuit to the coil of said line relay.

.3. In a telegraph system, a plurality of line relays, recording means, a local circuit, and a distributor having a plurality of segmented rings, alternate segments of one of said rings being arranged to operate said recording means and other segments in intervening phase relation with the previously mentioned alternate segments being connected through said local circuit to one of the coils of each of said line relays.

4. The combination with a standard two relay receiving circuit, of recording means and means synchronized with the unit intervals of the incoming signals for completing the biasing winding circuit of the receiving relays to operate said recording means independently of said relays.-

5. The combination with a standard two relay receiving circuit and means effective when both receiving circuit relays are in inoperative position to supply single unit im pulses, of means synchronized with the unit intervals of the incoming signals for completing the biasing winding circuit of the receiving relays.

6. In combination with a receiving circuit including a pair of line relays disposed in a line and biasing circuit, of a vibrating relay and a distributor, recording means connected to portions of said distributor, other portions thereof being incircuit with said biasing circuit, means for operating said vibrating relay and means rendered eifective upon the operation thereof to supply unit impulses to one of said recording means when he line current is less than the current in the biasing circuit.

7. In combination with a receiving circuit including a pair of line relays disposed in a line and biasing circuit, of a vibrating relayand a distributor, recording means connected to alternate portions of said distributor, other portions thereof being in circuit with said biasing circuit, circuit making and breaking means responsive to the operation of said vibrating relay for supplying unit impulses to said recording means during the I inoperative position of both of said first mentioned relays.

8. In combination with a receiving circuit including a pair of line relays disposed in a line and biasing circuit, of a vibrating relay and a distributor, a plurality of recording means connected to alternate portions of said distributor, other alternate portions thereof being in circuit with said biasing circuit, and means responsive to the operation of said vibrating relay to supply unit impulses to alternate recording means of said plurality during absence of line current.

.9. In an interpolating system, including, in combination, a receiving circuit having a pair of line relays, a distributor comprising a plurality of sets of segments, a vibrating relay connected to alternate portions of one of said sets, recording means associated with another of said sets, and means for operating two or more of said recording means when one of said line relays is inoperative.

10. In an interpolating system, including, in combination, a receiving circuit comprising a vpair of line relays, a distributor asso ciated therewith, a vibrating relay connected to alternate portions of said distributor, a printing relay controlled by either of said line relays or by said vibrating relay, recording means, and means operable to supply unit impulses from said printing relay to said recording means when both of said line relays are inoperative or to supply impulses greater than unit length and operate two or more of said recording means when one of,

said line relays is inoperative.

11. In an interpolating system, including, in combination, a receiving circuit comprising a pair of line relays, a distributor associated therewith, a vibrating relay connected to alternate portions of said distributor, a printing relay controlled selectively by either of said line relays or by said vibrating rela recording means, and means operable to supply unit impulses from said printing relay to said recording means when .both of said line relays are inoperative or to supply impulses greater than unit length and operate two or more of said recording means when one of said line relays is inoperative.

12. In an interpolating system, including, in combination, a receiving circuit having a pair of line relays each comprising an operating .and biasing winding, recording means and means for operating several of said recording means when the current in the operating winding in one of said line relays exceeds the current in its biasing winding at a time when the other line relay is inoperative.

13. In an interpolating system, including, in combination, a receiving circuit comprisa pair of line relays, recording means, and means dependent upon the operation of one of said line relays to supply impulses of more than unit length and render effective two or more of said recording means.

14. In an interpolating system, including, in combination, a receiving circuit comprising a pair of line relays and a vibrating relay, a plurality of recording means and means efiective in response to the operation of said vibrating relay to supply unit impulses to one of said recording means when both of said line relays are inoperative or to supply impulses of more than unit length when one of said line relays is unoperated to operate two or more recording means of said plurahty.

15. In an interpolating system, a receiving circuit comprising a line relay, distributor means co-operating with impulse storage and discharge means, a vibrating relay adapted to be operated by said storage and discharge means and in circuit with alternate portions of said distributor means, recording members, and means responsive to the operation of said vibrating relay and controlled by said distributor means for supplying a unit impulse to one of said recording members when said line relay is inoperative.

16. In combination, a receiving circuit ircluding a line relay disposed in a line and biasing circuit, a distributor to control said biasing circuit and thereby hold said line relay inoperative until proper strength of signal and proper phase relation of said distributor with respect to the line signals is reached.

17. In combination, a receiving circuit including a pair of line relays disposed in a line and biasing circuit, a distributor to control said biasing circuit and thereby main tain one of said relays operative, the signal strength having fallen below that necessary for initial operation of the said one of said relays, until proper phase relation of? said distributor with respect to the line signals is reached.

18. In combination, a receiving circuit including line relays connected in a line and biasing circuit, of a distributor, a vibrating relay connected in circuit with portions of said distributor, other portions (if said distributor co-operating with means to complete said biasing circuit and hold said line relays inoperative until the line current exceeds the current in the biasing circuit during synchronism of said distributor with received signals.

19. The herein described method of controlling an interpolating system comprising a receiving circuit including electro-magnetic means having windings disposed in a biasing and line circuit in combination with a distributor, which comprises, controlling the biasing circuit periodically to prevent the winding in circuit therewith from becoming efiective and restore the armatures of said electro-magnetic means to associated spacing contacts until proper phase relation of said distributor with respect to the line signals is reached.

20. The herein described method of controlling an interpolating system comprising a receiving circuit including a pair of polar relays having windings disposed in a biasing and line circuit, in combination with a distributor, which comprises, controlling the and during synchronism of said distributor with incoming signals.

21. The herein described method of controlling an interpolating system comprising a receiving circuit including a pair of polar relays having windings disposed. in a bias ing line circuit, in combination with a distributor, which comprises, controlling the biasing circuit intermittently to prevent the winding in circuit therewith from becoming effective and restore the armatures of said relays to associated spacing contacts when the line current is less than the current in said biasing circuit during synchronism of said distributors with incoming signals.

22. In an interpolating system, including, in combination, a pair of line relays disposed in a line and biasing circuit, and means for intermittently cont-rolling said biasing circuit to render said line relays inoperative.

23. In an interpolating system, including, in combination, relaymea-ns disposed in a line and biasing circuit, a vibrating relay, means for generating local impulses to op erate said vibrating relay, and means for intermittently controlling said biasing circuit to render said relay means inoperative.

24. In an interpolating system, including, in combination, normally unbiased relay means disposed in a line and biasing circuit and control means for intermittently removthe bias of said relay means and to render effective or ineffective said relay means.

25. In an interpolating system, including, in combination, a pair of line relays disposed in a line and biasing circuit, means for operating said recording means during the inoperative position of said line relays, means for operating said relays when the line current exceeds the biasing current, and means to intermittently control said biasing circuit to prevent restoration of said line relays while said recording means is being operated.

26. The combination with relay means disposed in a line and biasing circuit, of a dis tributor including electrical storage means, a vibrating relay adapted to be operated by said storage means, recording means, and means comprising an intermittent control for said biasing circuit and providing a relatively larger operating range for said recording means.

2?. In combination, a receiving circuit including a line relay disposed in a line and biasing circuit, a distributor to intermittently control said biasing circuit and to hold said line relay inoperative until a brush associated with said distributor has moved to a predetermined position.

28. In an interpolating system, a pair of line relays, a distributor having portions thereof disposed in a biasing circuit and other portions thereof connected to a recording member, means for rendering sald biasing circuit inefiective during the operation of said recording members, and means for restoring said line relays upon the completion of said biasing circuit when a brush associated with said distributor has moved beyond a segment thereof in circuit with a recording member.

29. In an interpolating system, a pair of line relays, a distributor having a set of segments, alternate segments of said set being disposed in a biasing circuit, other alternate segments thereof being connected to recording members, means for rendering said biasing circuit ineffective during the operation of said recording members, and means for restoring said line relays upon the completion of said biasing circuit when a brush associated with said distributor has moved beyond a segment thereof in circuit with a recording member and when the line current is less than the biasing current.

30. In an interpolating system, a pair of line relays, a distributor having a set of segments, alternate segments of said set being disposed in a biasing circuit, other alternate portions thereof being connected to a recording member, means for rendering said biasing circuit inefiective during the operation of said recording member, and means to restore said line relays before the brush of said distributor has reached a segment associated with a respective recording member.

MARK B. KERR. 

